Officials didn't disclosed the nature of the injuries, and replacements haven't been named.

UFC on FX 1 takes place Jan. 20 at Bridgestone Arena in Nashville, Tenn. UFC 143, meanwhile, takes place Feb. 4 at Mandalay Bay Events Center in Las Vegas. Officials hadn't announced if either fight is slated for the main cards, which airs on FX and pay-per-view, respectively.